This invention relates to eletric lamps and has particular pertinence to a baseless incandescent lamp, such as that of halogen-cycle type, combined with a plastic lamp base for vehicular use. Still more particularly, the invention pertains to an electric lamp assembly having metal-made coupling means providing for mechanical and electrical connection, as well as positional adjustment between the lamp and the lamp base.
The combination of a halogen-cycle incandescent lamp and a plastic lamp base is per se not new in the art but is disclosed in for example U.S. Pat. No. 4,412,273 to Helbig et al. The plastic lamp base permits manufacture at lower cost than metal-made ones and, moreover, provides a yieldable connection between the lamp and an automotive headlamp reflector which may be of an unyielding material. For connecting the lamp to the lamp base so as to permit adjustment of the lamp position, Helbig et al. employ a metal sleeve secured to the lamp, and a metal-made adjustment cap in which is seated the lamp and which is telescopically received in the sleeve. The telescoping sleeve and cap permit adjustment of the lamp filament or filaments so that light may be emitted in a predetermined pattern with respect to the base. With the adjustment completed, the sleeve and cap are welded together.
An objection to this prior art lamp assembly is that the telescoping sleeve and cap are, before being welded together, susceptible to both angular and axial displacements relative to each other. Such susceptibility of the mating parts to relative displacements has been prone to permit the lamp to go out of alignment with the lamp base before or during the welding of the sleeve and cap.